Goods are generally transported between locations by ship, train or truck. Many types of freight are conveniently housed in reusable shipping containers for transportation. A common form of shipping container is a metal box-shaped container with doors for access. Although the size and shape of shipping containers varies, a commonly used shipping container measures approximately 20 feet by 8 feet by 8.5 feet high (a “20 foot container”). Larger “40 foot” containers are also commonly used. These metal shipping containers generally have a timber floor, although metal floors and mixed timber and metal floors are also used.
Shipping containers are inspected by relevant authorities for cleanliness, integrity and suitability for the intended cargo before each use to ensure that they meet all the necessary regulations relating to the type of cargo to be carried. Regulations are particularly stringent when the goods are foodstuffs. Containers for foodstuffs must be free from cargo residue, infestation, odour, taint, transferable stains or rust, and flaking or blistering paint. The floor must be clean and dry.
A coating may be applied to the timber or metal floor of a shipping container to facilitate cleaning and overcome some of the problems associated with maintaining the integrity and cleanliness of the flooring. The application of a coating may form part of container refurbishment to upgrade a container for food grade use.
Solvent based coatings have been used on shipping container flooring to help overcome some of the problems associated with maintenance and cleaning of shipping containers. Coatings generally need to be replaced approximately every 12-18 months due to wear and tear. The coating process is time consuming. This has cost implications for the shipping company from the perspective of coating costs in addition to the time that the shipping container is unavailable for use.
In order to minimise the time when the shipping container is unavailable due to refurbishment, it is desirable that the floor coating can be applied quickly and cures as quickly as possible. A coating that cures completely overnight in a closed container is desirable. For this reason solvent based coatings have been used as they cure relatively quickly. A solvent based coating is generally applied to the floor surface by spraying. The application process is time consuming as the container walls must be covered up to prevent overspray. The person applying the coating will require a high level of personal protective equipment as the coating system is solvent based and will be used in a predominantly enclosed environment. It may be necessary to apply several coats to obtain a coating of adequate thickness. Each layer must be allowed to dry before the next layer is applied. These applied coatings may be slow to dry and leave residual, unacceptable odours.
A shipping container with solvent odour is unacceptable for food use, and it may take several days for the residual solvent odour to dissipate, thus extending the refurbishment period. Furthermore, a solvent based coating may be sensitive to water and high temperatures during the curing process, so use in a humid environment or high ambient temperatures may lead to unsatisfactory or unacceptable coatings.